Traditional optical fiber-based environmental detection system, for instance temperature measurement, can be achieved by using various optical fiber devices. Commonly used optical fiber devices include fiber Bragg gratings (FBGs), long-period fiber gratings (LPFGs) and fiber interferometers. Among them, FBGs are widely known for their small size and wavelength multiplexing capability, but the temperature sensitivity is relatively low (around 10 pm/° C.). LPFGs can have much higher sensitivity, but they suffer from cross-sensitivity to surrounding refractive index (SRI) and fiber bending. Optical fiber interferometers based on any of the cavity structures are highly sensitive, simple and relatively inexpensive. Some interferometric temperature sensors with sensitivity of about 12.9-118.6 pm/° C. have been demonstrated by splicing a section of multimode fiber (MMF) or thin-core fiber (TCF), or hollow core fiber (HCF) between two single-mode fibers (SMFs). Recently, to fill liquid with high thermo-optic coefficient into photonic crystal fiber (PCF) interferometers can achieve a highly sensitivity of nm/° C. order of magnitude. However, to fill liquid into the specific micro air holes of the PCF is quite complicated and a large SRI cross-sensitivity still exists.